Earth Systems

Earth Systems - 1 Earth Systems The water cycle Residence...

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1 Earth Systems The water cycle Residence time : how much time does a water molecule spend in a particular reservoir of the hydrosphere? o Reservoir and residence time Oceans, deep lakes, glacial ice – 1000 yrs Water trapped in deep rocks – 100,000 yrs Glaciers – 20-100 yrs Ground water – 100-200yrs Lakes – 50-100 yrs Rivers – 2-6months Atmosphere – 1-2 weeks Oceans and Seas ocean waters: characteristics o Differences notable in the surface layer o Dissolved minerals = 3.5% of total mass (main mineral nacl (sodium chloride)) => measure of salinity o Salinity affected by evaporation, precipitation and freshwater influx. High evaporation rate = high salinity Low evaporation rate = low salinity As a general pattern, salinity is low in equatorial regions It rises to a general maximum in the subtropics, where precipitation is low and evaporation extensive Decreases to a general minimum in the polar regions o Temperature
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2 Surface sea water generally decreases with increasing latitude 26 C(80 f) to -2C (28 F) ̊ Warmer on western margins Bottom waters always near freezing o Density Affected by temp, salinity, depth High temp = low density High salinity = high density Deep water has high density Ocean Waters: Movements o Tides Causes greatest vertical movements Some horizontal movement Caused by the gravitational attraction of the moon (lunar tides) and the sun (solar tides) Lunar tides = 2* solar tides All oceanic coastlines experience 2 high and 2 low tides about every 25 hrs Cycle of tidal fluctuation From its lowest point, the water rises gradually for 6 hrs and 13 mins, so that there is an actually movement of water toward the coast in what is called a flood tide.(high tide) Then the water begins to retract away from the coast for the next 6hrs and 13mins, this movement is called the ebb tide. (low tide) Causes the ocean to bulge Spring and Neap Tides o Each occurs twice a month
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3 Spring tides Sun – new moon – earth(above low tide)(horizontal – high tide) – full moon Bulge is greatest Neap Tides Sun – ¾ moon – earth (high tide – above and low tide – horizontal) Bulge is lower than normal tide range Perigee: when moon nearest to the earth Apogee: when moon farthest away from earth During perigee, tidal ranges are greater than during apogee. Tidal Range: the vertical diff in elevation between high and low tides. Enormous variations along different coastlines (0-15 m) Continental seacoasts have greater range Influenced by coastline shape and sea bottom Tidal bore: a wall of seawater o Currents Below the surface Large horizontal displacement of water Shifts vast quantity of water horizontally and vertically Influenced by ocean geometry and coriolis effect Surface currents : driven by wind flow Sub – surface currents (deep ocean circulation
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This note was uploaded on 01/30/2011 for the course 450 101 taught by Professor Rogerbalm during the Spring '08 term at Rutgers.

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Earth Systems - 1 Earth Systems The water cycle Residence...

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